WHAT’S UP DOC? Polio eradication

By Dr. Jeff Hersh/Daily News Correspondent

Tuesday

Feb 13, 2018 at 2:14 PM

Q: Is it true that the world is close to eradicating polio? Why not tetanus and other diseases as well?

A: There are many potential causes of infectious diseases that can be ‘spread’ or ‘caught’, including bacteria, viruses, fungi, prions and parasites. Infectious diseases can be spread from person to person (such as the flu, mononucleosis, polio, many others), animal to person (such a rabies, some types of flu such as ‘bird flu’, many others), or from inanimate objects (again such as the flu from touching a surface with active flu virus on it, or such things like tetanus which is from the bacterium Clostridium tetani which lives in soil and many other places, as well as many other diseases).

It is very hard, if not impossible, to eradicate diseases spread from sources where the infectious agent can ‘hide’ and survive in the environment, although preventing acute infection via vaccination from these diseases may be possible (as it is with tetanus).Infectious diseases where there is an animal reservoir for the diseases to ‘hide’ or ‘live’ in are also hard to eradicate as we would need to eradicate the disease in the animals (where it sometimes does not even cause symptoms); this is especially challenging if the disease can exist in wild animals (hence why eradicating rabies is so hard, although in closed conditions such as the island nations of Great Britain this has been possible).Diseases that only infect humans have the best chance of being eradicated. Smallpox is a great success story.

Poliomyelitis is caused by a virus that is shed in the stool of infected people. Poor sanitary conditions and poor hygiene contribute to its spread. After ingestion, the virus replicates in the nose/throat mucosa and/or the gastrointestinal (GI) tract of the patient. It then invades the lymph nodes and possibly spreads to the blood; in some cases it can also invade the neurons in the patient’s brain and/or spinal cord.

Polio infection is definitively diagnosed by cultures of certain body fluids or blood antibody tests. About 90 to 95 percent of those infected with the polio virus have minor non-specific symptoms such as low-grade fevers, malaise, sore throat and/or headache, and these people recover with no sequelae. Some people also have GI symptoms such as nausea, vomiting and/or abdominal pain, and again typically have a full recovery. About one percent of those infected develop paralytic polio (damage to muscle innervating neurons), causing muscle weakness (most often in one limb or on one side of the body) which can progress to flaccidity and paralysis. Although there is no cure for polio, about half of these patients recover fully on their own, a quarter have mild residual weakness and about a quarter have severe permanent disability. Overall, the prognosis is better for younger children.

The reasons that polio is a good candidate for eradication include:

It is passed only from human to human (via contaminated waste products), so if we could get everyone on the planet immunized we could potentially break the cycle of someone getting the condition and passing it on to someone else.The polio vaccines (there are several different ‘strains’ of it, and eradication requires addressing all the strains) are relatively inexpensive, making an effort to eradicate it possible.There is potential for ‘herd immunity’, where a large enough percentage of the population is vaccinated so as to prevent the disease from ‘going around.’

The plan to eradicate polio being led by the Global Eradication Partnership (which includes the World Health Organization, the Centers for Disease Control in the U.S., the United Nations Children’s Fund, Rotary International and the Bill and Melinda Gates Foundation) is based on the following four-prong approach:

Routine infant immunization: this must include developing nations where routine infant care may be limitedSupplementary immunizations for places where infant immunization was not able to be achieved (with programs such as National Immunization Days to try to increase herd immunity)Surveillance for outbreaks (to focus immunization and other efforts to prevent further spreading)“Mop-up” campaigns to address areas where an outbreak may have occurred.

Although the job is not yet completed, the number of people affected by polio has dramatically decreased. In 1988 there were more than 350,000 cases of polio worldwide, by 2013 this had decreased to less than 1000.

There are challenges in overcoming the last hurdles to achieve complete eradication:

Variable commitment from nations where there are still outbreaksSurveillance gaps that allow outbreaks to go unidentifiedFunding limitationsScientific limitations, such as limitations in the overall effectiveness of the available vaccines.

We must avoid the closed minded thinking that this is a developing nation issue and not one we need think about in the U.S. This is not true; the world has gotten smaller and we have seen diseases that we thought were not an issue in the U.S. eventually emerge here, for example West Nile Virus. We must think globally if we are to insure the health of the planet, as well as the health of our own population.